Performance of CT-based low skeletal muscle index, low mean muscle attenuation, and bioelectric impedance derived low phase angle in the detection of an increased risk of nutrition related mortality

Abstract

The aim of this study was to evaluate in a head to head comparison the performance of bioimpedance derived low phase angle (PA), CT-based low skeletal muscle index (SMI) and low mean muscle attenuation (MA), and Pandora Score (PS) to detect an increased nutrition related mortality in hospitalized patients. A total of 7736 patients were hospitalized in Dessau community hospital (Nov 11, 2016-Feb 05, 2017). In 227/7736 patients an abdominal CT scan was obtained and low values (below threshold) of skeletal muscle index (SMI) and mean muscle attenuation (MA) were obtained at L3 level using Slice-O-Matic. In 180/227 patients, malnutrition screening (NRS-2002≥3), determination of low PA (<5th percentile) and calculation of 30-day mortality risk (PS≥5%) were done within 6 days after the CT scan. PA was low in 116 (64%), SMI was low in 95 (53%), and MA was below threshold in 137 (77%) patients. Using hospital mortality (8.3%) as a gold standard, low SMI, low MA, or low PA showed high sensitivity (SMI 93.3%; MA 86.7%; PA 86.7%) and high negative predictive (NPV) values (SMI 98.9%; MA 95.3%; PA 96.9%) and improved specificity (NRS+SMI 65.5%; NRS+MA 50.3%; NRS+PA 50.3%) when combined with the criterion NRS≥3. Using hospital mortality as a gold standard, a PS≥36 (predicted mortality≥5%) showed a sensitivity of 73.3%, a specificity of 62.2% and an NPV of 96.4%. PS predicted mortality was ≥5% in 70 (39%) patients and was higher (median 5.2%; IQR: 2.8; 11.8 vs 1.7%; IQR: 1.0; 2.8; p<0.001) in patients with a low PA and this was also observed for low vs normal SMI (median 5.7%; IQR: 2.6; 11.1 vs 2.7%; IQR:1.4;5.5; p<0.001) but not for low vs normal MA (median 3.9%; IQR: 2.1; 8.8 vs 3.4%; IQR: 2.0; 8.1; ns). Determination of phase angle<5th percentile is a convenient non-invasive and inexpensive bedside method with high sensitivity and a high negative predictive value to detect patients at risk of nutrition related mortality with a performance comparable to CT derived skeletal muscle index or mean muscle attenuation.